cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

Showing 1-5 of 5 results.

A032006 "AFK" (ordered, size, unlabeled) transform of 2,1,1,1,...

Original entry on oeis.org

1, 2, 1, 5, 5, 7, 19, 21, 33, 41, 101, 109, 175, 231, 321, 623, 761, 1087, 1495, 2109, 2661, 4985, 5849, 8557, 11251, 15831, 20373, 27743, 44357, 55135, 76123, 101373, 136689, 178673, 240125, 303997, 475183, 578271, 793809, 1024991, 1387985, 1763719, 2363671
Offset: 0

Views

Author

Keywords

Comments

Number of compositions of n into distinct parts if there are 2 kinds of part 1. a(3) = 5: 3, 21, 21', 12, 1'2.

Crossrefs

Programs

  • Maple
    b:= proc(n, i, p) option remember;
          `if`(n=0, p!, `if`(i<1, 0, b(n, i-1, p)+
          `if`(i>n, 0, `if`(n=1, 2, 1)*b(n-i, i-1, p+1))))
        end:
    a:= n-> b(n$2, 0):
    seq(a(n), n=0..45);  # Alois P. Heinz, Sep 05 2015
  • Mathematica
    b[n_, i_, p_] := b[n, i, p] = If[n == 0, p!, If[i < 1, 0, b[n, i - 1, p] + If[i > n, 0, If[n == 1, 2, 1]*b[n - i, i - 1, p + 1]]]];
    a[n_] := b[n, n, 0];
    a /@ Range[0, 40] (* Jean-François Alcover, Sep 11 2019, after Alois P. Heinz *)
  • PARI
    seq(n)={apply(p->subst(serlaplace(p), y, 1), Vec((1 + 2*x*y)*prod(k=2, n, 1 + x^k*y + O(x*x^n))))} \\ Andrew Howroyd, Jun 21 2018

Extensions

a(0)=1 prepended by Alois P. Heinz, Sep 05 2015

A032007 "AFK" (ordered, size, unlabeled) transform of 1,2,3,4,...

Original entry on oeis.org

1, 1, 2, 7, 10, 25, 68, 111, 208, 435, 1218, 1773, 3586, 6077, 12156, 31961, 47624, 86825, 151962, 265525, 469610, 1242607, 1750108, 3217663, 5263928, 9205197, 14713474, 26440503, 63610938, 90877893, 159360628, 258871127, 431309688, 687140639, 1134231986
Offset: 0

Views

Author

Keywords

Comments

Sum of products of parts in all compositions of n into distinct parts. - Vladeta Jovovic, Feb 21 2005
Number of compositions of n into distinct parts if there are i kinds of part i. a(3) = 7: 3, 3', 3'', 21, 2'1, 12, 12'.

Crossrefs

Programs

  • Maple
    b:= proc(n, i, p) option remember;
          `if`(n=0, p!, `if`(i<1, 0, b(n, i-1, p)+
          `if`(i>n, 0, i*b(n-i, i-1, p+1))))
        end:
    a:= n-> b(n$2, 0):
    seq(a(n), n=0..40);  # Alois P. Heinz, Sep 05 2015
  • Mathematica
    b[n_, i_, p_] := b[n, i, p] = If[n == 0, p!, If[i < 1, 0, b[n, i - 1, p] + If[i > n, 0, i*b[n - i, i - 1, p + 1]]]];
    a[n_] := b[n, n, 0];
    a /@ Range[0, 40] (* Jean-François Alcover, Sep 11 2019, after Alois P. Heinz *)
  • PARI
    seq(n)={apply(p->subst(serlaplace(p), y, 1), Vec(prod(k=1, n, 1 + k*x^k*y + O(x*x^n))))} \\ Andrew Howroyd, Jun 21 2018

Extensions

a(0)=1 prepended by Alois P. Heinz, Sep 05 2015

A032008 "AFK" (ordered, size, unlabeled) transform of 1,3,5,7,...

Original entry on oeis.org

1, 1, 3, 11, 17, 53, 161, 285, 569, 1459, 4699, 7177, 15631, 28229, 66883, 211311, 319929, 627705, 1163049, 2150209, 4422225, 14320583, 20392019, 39962165, 68618087, 126643545, 212615483, 433704811, 1312156393, 1864959757, 3502343041, 5919183485, 10364053441
Offset: 0

Views

Author

Keywords

Comments

Number of compositions of n into distinct parts if there are (2i-1) kinds of part i. a(3) = 11: 3, 3', 3'', 3''', 3'''', 21, 2'1, 2''1, 12, 12', 12''. - Alois P. Heinz, Sep 05 2015

Crossrefs

Programs

  • Maple
    b:= proc(n, i, p) option remember;
          `if`(n=0, p!, `if`(i<1, 0, b(n, i-1, p)+
          `if`(i>n, 0, (2*i-1)*b(n-i, i-1, p+1))))
        end:
    a:= n-> b(n$2, 0):
    seq(a(n), n=0..40);  # Alois P. Heinz, Sep 05 2015
  • Mathematica
    b[n_, i_, p_] := b[n, i, p] = If[n == 0, p!, If[i < 1, 0, b[n, i - 1, p] + If[i > n, 0, (2 i - 1)*b[n - i, i - 1, p + 1]]]];
    a[n_] := b[n, n, 0];
    a /@ Range[0, 40] (* Jean-François Alcover, Sep 11 2019, after Alois P. Heinz *)
  • PARI
    seq(n)={apply(p->subst(serlaplace(p), y, 1), Vec(prod(k=1, n, 1 + (2*k-1)*x^k*y + O(x*x^n))))} \\ Andrew Howroyd, Jun 21 2018

Extensions

a(0)=1 prepended by Alois P. Heinz, Sep 05 2015

A032043 "BFK" (reversible, size, unlabeled) transform of 2,2,2,2...

Original entry on oeis.org

1, 2, 2, 6, 6, 10, 34, 38, 62, 90, 306, 334, 574, 794, 1226, 3390, 4014, 6370, 9130, 13598, 18470, 48114, 55290, 88966, 123238, 184178, 245714, 358710, 771990, 937210, 1427698, 1992662, 2882894, 3895626, 5533314, 7318270, 14935246
Offset: 0

Views

Author

Keywords

Crossrefs

a(n) = (A032005(n) + 2)/2.

Programs

  • PARI
    seq(n)={apply(p->subst(serlaplace(p + polcoeff(p,1)), y, 1)/2, Vec(y-1+prod(k=1, n, 1 + 2*x^k*y + O(x*x^n))))} \\ Andrew Howroyd, Jun 21 2018

Extensions

a(0)=1 prepended by Andrew Howroyd, Jun 21 2018

A355387 Number of ways to choose a distinct subsequence of an integer composition of n.

Original entry on oeis.org

1, 2, 5, 14, 37, 98, 259, 682, 1791, 4697, 12303, 32196, 84199, 220087, 575067, 1502176, 3923117, 10244069, 26746171, 69825070, 182276806, 475804961, 1241965456, 3241732629, 8461261457, 22084402087, 57640875725, 150442742575, 392652788250, 1024810764496
Offset: 0

Views

Author

Gus Wiseman, Jul 04 2022

Keywords

Comments

By "distinct" we mean equal subsequences are counted only once. For example, the pair (1,1)(1) is counted only once even though (1) is a subsequence of (1,1) in two ways. The version with multiplicity is A025192.

Examples

			The a(3) = 14 pairings of a composition with a chosen subsequence:
  (3)()     (3)(3)
  (21)()    (21)(1)   (21)(2)    (21)(21)
  (12)()    (12)(1)   (12)(2)    (12)(12)
  (111)()   (111)(1)  (111)(11)  (111)(111)
		

Crossrefs

For partitions we have A000712, composable A339006.
The homogeneous version is A011782, without containment A000302.
With multiplicity we have A025192, for partitions A070933.
The strict case is A032005.
The case of strict subsequences is A236002.
The composable case is A355384, homogeneous without containment A355388.
A075900 counts compositions of each part of a partition.
A304961 counts compositions of each part of a strict partition.
A307068 counts strict compositions of each part of a composition.
A336127 counts compositions of each part of a strict composition.

Programs

  • Mathematica
    Table[Sum[Length[Union[Subsets[y]]],{y,Join@@Permutations/@IntegerPartitions[n]}],{n,0,6}]
  • PARI
    lista(n)=my(f=sum(k=1,n,(x^k+x*O(x^n))/(1-x/(1-x)+x^k)));Vec((1-x)/((1-2*x)*(1-f))) \\ Christian Sievers, May 06 2025

Formula

G.f.: (1-x)/((1-2*x)*(1-f)) where f = Sum_{k>=1} x^k/(1-x/(1-x)+x^k) is the generating function for A331330. - Christian Sievers, May 06 2025

Extensions

a(16) and beyond from Christian Sievers, May 06 2025
Showing 1-5 of 5 results.